Mass occupant notification is the capability to provide real-time information and instructions to people in a particular geographic region, building, area, site, campus, installation, manufacturing plant or other facility using intelligible voice communications. The voice communications may be accompanied by visible signals, text and graphics, and possibly other communication methods. Mass occupant notification (MON) systems, which also may be referred to herein as emergency alert notification systems, are intended for the protection of life by indicating the existence of an emergency situation and instructing people of the necessary and appropriate response and action.
MON systems in use today include Wide Area MON systems and Individual Building MON systems. Individual Building MON systems are used in providing real-time information to personnel within buildings and in the immediate vicinity of buildings. In some cases, Individual Building MON systems are integrated with fire alarm and public address systems in buildings. These systems may include strobe lights as well as siren and speaker systems for indicating and announcing emergency alerts. Wide Area MON systems are used in providing real-time information to personnel in outdoor areas, such as on military installations and campuses. Wide Area MON systems normally include two or more central control stations which may or may not be in communication with individual building MON systems and regional or national command systems. Most Wide Area MON systems generally include outdoor high-power speaker arrays and siren systems which provide voice signals, music and alarm tones. The high-power speaker arrays are usually arranged into zones so that each zone can be individually controlled by a control station.
Some MON systems use terrestrial wireless FM communication links to communicate information between control stations and speaker arrays located in remote portions of the covered area. However, the performance of these FM links has been less than desirable. One problem with the terrestrial FM links is latency in the timing of the alerts messages. For example, speaker arrays located near a control station may receive the alerts slightly sooner than speaker arrays located farther from the control station. This causes the audio messages broadcast from widely separated speaker arrays to be out of phase, which degrades the intelligibility of the audio messages.
What is needed, therefore, is MON system which provides robust and reliable communication links between a source of an alert and widely-scattered remote speaker locations, and which provides alert messages to all of the remote speaker locations at substantially the same time.